A new oral recombinant vaccine protects children against infection with Helicobacter pylori, researchers from China report.

At least half the world’s population is affected by H. pylori, and so far none of several H. pylori vaccine candidates have proven effective in humans.

Dr. Quan-Ming Zou from Third Military Medical University in Chongqing and colleagues developed an oral recombinant H. pylori vaccine using urease B subunit fused with heat-labile enterotoxin B subunit and tested its effectiveness in a phase 3 trial of nearly 4,500 healthy children without past or present H. pylori infection.

Based on confirmed H. pylori infections, the three-dose vaccine schedule provided efficacy rates of 71.8 percent in year one, 55.0 percent in year two, and 55.8 percent in year three after vaccination.

One month after the third dose, children in the vaccine group had significantly higher serum immunoglobulin (Ig) G and salivary IgA seroconversion rates than did children in the placebo group, the researchers report in The Lancet.

Only 7 percent of children in each group experienced at least one adverse reaction, and all such reactions were mild and resolved within 24 hours. There were no serious adverse events attributed to the vaccine.

“The sustained vaccine protection against H. pylori infection up to three years suggests that this vaccine could substantially reduce the incidence of H. pylori-associated gastritis, gastric ulcer, duodenal ulcer, and gastric adenocarcinoma,” the researchers concluded. “However, longer follow-up in the vaccinated cohort would be warranted to provide direct evidence of the vaccine protection against H. pylori-associated diseases. Furthermore, booster doses at appropriate timing might be needed for long-term protection.”

Dr. Philip Sutton from Murdoch Childrens Research Institute at Royal Children’s Hospital in Parkville, Australia, who wrote an accompanying editorial, said he was surprised by the findings.

“It is quite surprising the vaccine produced some protection,” he told Reuters Health. “The H. pylori vaccine field has been quite depressed for many years, mostly because of the failure of previous vaccine trials to produce protection. Hence the protection reported was a welcome surprise. The antigen and adjuvant used were also not anything really new and have been tried before, so it was surprising this particular formulation produced protection.”

In his editorial, Dr. Sutton stressed that “H. pylori infections mostly happen throughout childhood, so a vaccine ideally needs to protect for 10–15 years and more.”

He concluded, “This outcome will hopefully rekindle interest in this important topic, and encourage increased investment in progression of new projects through to advanced clinical trials.”

Dr. Miguel O’Ryan from the University of Chile in Santiago recently reviewed persistent and transient H. pylori infections in childhood. He told Reuters Health by email, “In regions similar to Chile, infection with H. pylori that will persist over time will most probably be acquired within the first three years of life. The great majority of these children will not develop symptoms within the following three to five years. It remains to be seen how many will develop any disease later in life.”

“Our data suggests that if H. pylori persistence is the main trigger for diseases later in life (cancer or ulcer or both) in a subset of individuals, vaccination to avoid infection (similar to the papilloma virus approach) would have to occur before two years of age,” Dr. O’Ryan said.

“At the moment, information available does not suggest that these children should be treated but this may change for subsets of children, if we can identify early markers for future disease,” he concluded.

Chongqing Kangwei Biological Technology funded the trial and employed one of the 22 authors.

Dr. Zou did not respond to a request for comments.